Biological membranes + Cell DDD

Question 1

What is the function of a cell memebrane

Answer 1

membranes form barriers and separate the cell contents from the cells exterior environment. Or separate organelles from the cytoplasm, they need to allow some molecules through, into or out of the cell. So some membranes also have permeability.

Question 2

What is permeability

Answer 2

Permeability refers to the ability to let substances pass through. Some very small molecules simply diffuse through the cell membrane, in its structural molecules. Some substances dissolve in the lipid layer and simply pass through. And finally some substances pass through through special protein channels or carriers.

Question 3

What type of permeability do plasma cell membranes have and why ?

Answer 3

Partially permeable- only allow some substances through. The properties of the membranes components determines its permeability. For example how many proteins it contains, ect.

Question 4

What is the role of membranes at the surface of cells

Answer 4

The plasma membrane: separates the cells components from its external environment (in single celled organisms the environment is its external environment) the membrane regulates the transport of materials in and out of the cell. It may also contain enzymes involved in many metabolic pathways. They also have antigens so that the organisms immune system can recognise the cell as self and not attack it. Finally, membranes may release chemicals to other cells.

Question 5

What is the role of membranes within cells

Answer 5

The membranes found around organelles in eukaryotic organisms separate the cell contents from the cytoplasm so each organelle is its own discrete entity. For example, mitochondria have a folded inner membrane called cristae, this gives large surface areas for the reactions of aerobic respiration.
As well as this, chloroplasts have inner membranes called thylakoids, which house chlorophyll. On these membranes stages of photosynthesis occurs.

Question 6

State the fluid mosaic model of cell membrane structure

Answer 6

In 1972, singer and Nicholson proposed a model that allowed the passage of molecules through the membrane. Their structure explained how membranes could be more dynamic and interact more with the cells environment. It was called the fluid mosaic model. And proposed that the fabric of the membrane consisted of a phospholipid bi-layer. With proteins embedded floating within it, making up a mosaic pattern. The lipid molecules can change places with each other, and some proteins move giving it more fluidity. The fabric of the membrane, made out of the lipid bilayer, have their hydrophilic polar heads on contact with the water exterior and interior of the cell. The hydrophobic tails are then tucked away inside the membrane.

Question 7

State and Describe the various proteins involved within membranes

Answer 7

Some of the proteins have pores and act as channels to allow ions, which have an electrical charge and are surrounded by water molecules, to pass through.
Some of the proteins are carriers and, by changing their shape, carry specific molecules across the membrane.
And finally, other proteins may be attached to the carrier proteins and function as enzymes, antigens or receptor sites for complementary-shaped signalling molecules such as hormones.

Question 8

What is the function of cholesterol in membranes

Answer 8

The function of cholesterol in the cell membrane is to stabilize the interactions between the phospholipids and prevent the membrane from getting too fluid or too flexible. It also resists temperature changes on the structure of the membrane.

Question 9

What is the total thickness of the cell membrane

Answer 9

Between 5 and 10 nm

Question 10

What is the glycocalyx

Answer 10

The glycocalyx is outside the membrane of cells and is formed by carbohydrate chains attached to either lipids (glycolipids) or proteins (glycoprotein) in the membrane.

Question 11

Describe the different compositions of cell membranes in neurones, white blood cells and root hair cells

Answer 11

In neurone, the protein channels and carriers in the plasma membrane covering the long axon allow entry and exit of ions to bring about the conduction of electrical impulses along their length. As well as this they have a myelin sheath formed by flattened cells wrapped around them several times, giving several layers of cell membrane. This is about 20 percent proteins and 76 percent lipids, making the axon incredibly insulated.

The plasma membrane of white blood cells contain special protein receptors that enable them to recognise the antigens on foreign cells, usually from invading pathogens but also from tissue or organ transplants.

Root hair cells in plants have many carrier proteins to actively transport nitrate ions from the soil and into cells

The inner membranes of mitochondria are 76 % protein and 24 % lipid. This is because their inner membrane contain many electron carriers that are made of protein, and hydrogen ion channels associated with ATP synthase enzymes.

Question 12

What is simple diffusion and describe its process

Answer 12

All molecules have kinetic energy and can move freely and randomly within gas or liquid media. This will happen even if the medium is not mixed by stirring or shaking. If there is a higher concentration of a certain type of molecule in an area, then the molecules will bump into eachother as they randomly move, and eventually they will spread further from each-other. More will move to an area of low concentration, until eventually they become evenly dispersed. They reach equilibrium as there is no net movement. Some molecules which are small and non polar can pass through membranes by this process of simple diffusion. A-swell as this, fat-soluble molecules such as steroid hormones, even if they are larger, can diffuse through as they dissolve in the lipid bilayer.

Question 13

How do water molecules diffuse across plasma membranes

Answer 13

Water molecules are a special case. Since they are polar and insoluble in the lipid bi layer it would seem impenetrable. However water, is present in such great concentrations that significant direct diffusion does happen. In membranes where a very high rate of water molecules are required there may be specific water channel proteins known as aquaporins. These allow water across the membranes without moving through lipid environment.

Question 14

How is concentration maintained and give two examples

Answer 14

Many molecules entering cells then pass into organelles are used for metabolic reactions: this maintains a concentration gradient and keeps more molecules entering cells. For example. Oxygen diffusing into the cytoplasm of respiring cells then diffuses into mitochondria and is used for aerobic respiration.
As well as this carbon dioxide diffusing into palisade mesophyll cells of plants will then diffuse into chloroplasts and can be used for photosynthesis.

Question 15

What factors effect the rate of simple diffusion

Answer 15

Simple diffusion relies only on the molecules’ own kinetic energy. And so factors that alter thus kinetic energy will effect this rate of diffusion. For example temperature. As temp increases, molecules have more kinetic energy so their rate if diffusion will increase. Conversely, if they loose heat rate of diffusion slows down.
-diffusion distance, the thicker the membrane across which molecules have to diffuse, the slower the diffusion rate
-surface area, more diffusion can take place across a larger surface area. Cells specialised for absorbsion have extensions to increase their surface area. For example microvilli.
-size of diffusion molecule- smaller ions or molecules diffuse more rapidly than larger molecules
-concentration gradient- the steeper this gradient the faster the diffusion to the side with fewer molecules.

Question 16

What is facilitated diffusion

Answer 16

Facilitated diffusion is a type of diffusion in which the molecules move from the region of higher concentration to the region of lower concentration assisted by a carrier. It occurs when small molecules have polarity, such as ions with an electrical charge so they cannot pass through the lipid bilayer due to the hydrophilic and hydrophobic tails and heads.

Question 17

What protein support diffusion do neurone have

Answer 17

Neurone plasma membranes have many channels specific to either sodium or potassium ions. The diffusion of these ions into and out of the neuron axon is crucial to the conduction of nerve impulses. At synapses, there are also calcium ion channels.

Question 18

What protein support diffusion do epithelial cells have

Answer 18

The plasma membranes of epithelial cels that line your airways have chloride ion channels, and these play a crutial role in regulating the composition of mucus to trap particles and pathogens.

Question 19

What is the function of the transport protein: channel protein

Answer 19

They create hydrophilic channels to transport polar molecules and ions that cannot pass through the hydrophobic tails of the phospholipid bilayer. It is a type of facillitated diffusion and it is never an active process.

Question 20

What is the function of the transport protein: carrier proteins

Answer 20

Specific to particular ions or molecules that are too large to fit through phospholipids. This is a type of facilitated diffusion that is active, as it uses ATP to help with it conformational change.

Question 21

What is the term for when a molecule has both hydrophobic and hydrophilic areas

Answer 21

Amphipathic

Question 22

What is the function of glycolipids

Answer 22

Glycolipids are carbohydrates attached to the hydrophilic phosphate group head. It helps in cell signalling and recognition.

Question 23

Define the term osmosis

Answer 23

Osmosis is the net movement of water molecules from an area of high water potential to low water potential across a partially permuable membrane.

Question 24

What is water potential

Answer 24

Water potential is the measurement of the tendency of water molecules to diffuse from one region to another

Question 25

What happens when solute molecules are added to water

Answer 25

When solute molecules are added to water, the relative number of water molecules, in the resulting solution, is changed. If the solute molecules dissociate into charged ions such as sodium chloride dissociating into sodium and chloride ions, they exert more effect on the relative number of water molecules than do larger but non polar molecules such as glucose. This is because, the number of particles in the solution doubles and water molecules are attracted to them and prevent them from crossing the membrane because they become to large of molecules.

Question 26

What is the water potential of pure water

Answer 26

O kPa

Question 27

What happens to water potential as solute molecules are added

Answer 27

When solute molecules are added, they lower the pater potential of the solution. The more solute molecules in the solution, the lower the water potential.

Question 28

What are the units for measuring water potential

Answer 28

Water potential is measured in kilopascal (kPa) pure water has the highest potential possible of 0kPa.

Question 29

What happens when a cell is placed into an area of higher water potential.

Answer 29

The water potential inside cells is lower than that of pure water, as there are solutes in solution, in the cytoplasm and inside the large vacuole of plant cells. When the cells are placed in a solution of higher water potential, then water molecules move by osmosis down the water potential gradient,across the plasma membrane, into the cell.

Question 30

What is the term for when in an animal cell, a lot of water enter the cell. It will then swell and burst as the plasma membrane breaks.

Answer 30

Cytolysis

Question 31

What is the term for a plant cell when the cell swells up to a certain size, but the cell wall prevents the cell bursting

Answer 31

Turgid

Question 32

What is the term for when an animal cell has lost water due to water potential outside the cell being higher than inside the cell, and it becomes shrivelled

Answer 32

Crenated

Question 33

What is the term for when a plant cells cell membrane shrinks and it pulls away from the cell wall.

Answer 33

Plasmolysed (plant tissue with plasmolysed cells is described as flaccid)

Question 34

during active transport, where do cells get energy from to carry this out

Answer 34

The energy is provided from the hydrolysis of ATP

Question 35

Why do carrier proteins carry out active processes of diffusion

Answer 35

These membrane proteins have specific regions, or sites that combine reversible with only certain molecules or ions. They also have a region that binds to and allows the hydrolysis of a molecule of ATP, to release energy, and in this way they act as enzymes. The energy helps the carrier proteins change its conformation, and in doing so it carries the ion from one side of the membrane to the other. For example in guard cells, ATP made by chloroplasts provides energy to actively transport potassium ions from surroundings into the Gard cells. This influx of ions lowered the water potential in the cells so that water enters by osmosis. As the guard cell swells, their tips bulge which opens the stomata.

Question 36

What is bulk transport

Answer 36

Some cells need to transport large molecules and particles too large to pass through plasma membrane, in or out. They do this by bulk transport, a process that requires energy from ATP. The energy released from the hydrolysis of ATP enables the sodium potassium pump protein to change its shape so that 3 sodium ions are now on the outside of the cell and 2 potassium ions are on the inside of the cell.

Question 37

What is meant by the term, endocytosis

Answer 37

This is how large particles may be brought into a cell. They do not pass through the plasma membrane. Instead, a segment of the plasma membrane surrounds and encloses the particle and brins it into the cell, enclosed inside a vesicle. For example in phagocytosis. However, ATP is needed to provide energy to form the vesicles and move them, using molecular motor proteins, along cytoskeleton threads into the cells exterior.

Question 38

What is meant by the term, exocytosis

Answer 38

This is how large molecules may be exported out of the cells. They do not pass through the plasma membrane. Instead a vesicles containing them is moved towards and then fuses with the plasma membrane. An example of this is seen at synapses. Where chemicals in vesicles are moved by motor proteins along cytoskeleton threads, to the presynaptic membrane, here the vesicles fuse with the membrane and the neurotransmitter chemicals are released into the synaptic cleft. In this case. ATP is needed to fuse the membranes together as well for moving the vesicles. Molecule of ATP is needed for every step motor proteins take along cytoskeltal threads.

Question 39

What happens in the case of phospholipids when loosing temperature (Bi-layer)

Answer 39

-saturated fatty acids become compressed -however,there are many unsaturated fatty acids making up the cell membrane. And as they become compressed, the kinks in their tails push the adjacent phospholipid molecules away. This maintains membrane fluidity. -therefore, the proportions of unsaturated and saturated fatty acids within a cells membrane, determine the membranes fluidity at colder temperatures. -cholesterol in the membrane also buffers the effect of lowered temperature, to prevent a reduction in the membranes fluidity. It does this by preventing the phospholipid molecules from packing together too closely, because cholesterol molecules are between groups of phospholipid molecules.

Question 40

What happens in the case of phospholipids when temperature increases (bi-layer)

Answer 40

-the phospholipids acquire more kinetic energy and move around, in a more random way. This increases membrane fluidity, aswell as permeability. -it also affects the way membrane-embedded proteins are positioned and may function. If some of the proteins that act as enzymes in a membrane drift sideways, this could alter the rate of reaction they catalyse. -the presence of cholestorol molecules buffers the effects of increasing heat and reduces the increase of membrane fluidity. - an increase in membrane fluidity may effect the plasma membrane during phagocytosis. -the increase in membrane fluidity may also change the ability of cells to signal each other by releasing chemicals, often by exocytosis.

Question 41

What happens if membrane structures are distrusted buy high tempratures above proteins optimum temperature

Answer 41

Proteins are not as stable as lipids. So high temperatures cause the atoms within there large molecules to vibrate, and this breaks their hydrogen bonds and ionic bonds that hold their structure, causing the proteins to unfold. Their tertiary structure changes and they cannot change back again as they are denatured. As well as this just under the plasma membrane are cytoskeleton threads made of protein. If both types of proteins are denatured, then the membrane will begin to fall apart and it will become very permeable.

Question 42

What are the three key stages of the cell cycle

Answer 42

Interphase Nuclear division (mitosis or meiosis) Cytokinesis

Question 43

Describe the processes involved with interphase stage: G1

Answer 43

G1- proteins synthesis occurs to make proteins involved in synthesising organelles -the organelles replicate -cell is checked that it is the correct size, has the correct nutrients,growth factors ad that there i no damaged DNA. If check is not passed, replication doesn’t continue.

Question 44

Describe the processes involved with the interphase stage: S

Answer 44

-DNA is replicated Once the cell has entered this stage it is committed to finishing the cycle.

Question 45

Describe the processes involved in the interphase stage: G2

Answer 45

-cell grows And special chemicals ensure the cell is ready for mitosis by stimulating proteins that will be involved in making chromosomes condense and in formation of the spindle.

Question 46

What is the significance of mitosis in the life cycle

Answer 46

All living organisms need to produce genetically indentical daughter cells, by mitosis, for the following reasons. -asexual reproduction- single celled protoctists such as amoeba and paramecium divide by mitosis to produce new individuals. Some plants such as strawberry plants reproduce asexually by forming new plantlets at the ends of stolons. As well as this aphids may produce eggs that dont need fertilising. -growth- all multicellular organisms grow by producing cels that are genetically identical to each other and the parent cell from which they arose by mitosis. -tissue repair- wounds heal when growth factors, secreted by platelets and macrophages and damaged cells. Of the blood vessels walls stimulate the proliferation of endothelial and smooth muscle cells to repair damaged blood vessels.

Question 47

What are the four stages of mitosis

Answer 47

Prophase Metaphase Anaphase Telophase

Question 48

Describe the events involved in prophase of mitosis

Answer 48

-the chromosomes that have replicated during s phase of interphase and consist of two identical sister chromatids, now shorten and thicken as the DNA supercoils. -the nuclear envolope breaks down -the contrôle in animal cells divides and the two new daughter centrioles move to opposing poles of the cell. -cytoskeleton tubulin threads form a spindle between these centrioles. The spindle has a 3D structure and is rather like line of longitude on a virtual globe. In plat cells, the tubulin threads are formed by the cytoplasm not centrioles.

Question 49

Describe the events involved in metaphase of mitosis

Answer 49

-the pairs of chromatids attach to the spindle threads at the equator reigon -they attach by their centromeres

Question 50

Describe the events involved in anaphase of mitosis

Answer 50

-the centromere of each pair of chromatids splits. -motor proteins walking along the tubulin threads, pull each sister chromatid as a pair, in opposite directions towards the poles. -because the centromere goes first, we now refer to them as chromosomes because of the v like shape

Question 51

Describe the events involved in telophase of mitosis

Answer 51

-the separated chromosomes reach the poles -new nuclear envolopes form around each set of chromosomes -the cell now contains two nuclei each genetically identical to each other and to the parent cell to which they arose from.

Question 52

What is cytokinesis

Answer 52

Once mitosis is complete, the cell splits into two, so that each new cell contains a nucleus. This is called cytokinesis. In animal cells, the plasma membrane folds inwards and nips in the cytoplasm. However in plant cells, an end plate forms where the equator of the spindle was, the new plasma membrane and cellulose cell wall material are laid down on either side along this end plate. Two new daughter cells are formed that are genetically identical

Question 53

What does the term diploid mean

Answer 53

Diploid is a term that refers to the presence of two complete sets of chromosomes in an organism's cells, with each parent contributing a chromosome to each pair. Humans are diploid, and most of the body's cells contain 23 chromosomes pairs. Meaning 46 chromosomes

Question 54

What is the significance of meiosis in life cycles

Answer 54

Sexual reproduction increases genetic variation, because it involves the combining of genetic material from two unrelated individuals of the same species, by the process of fertilisation. Genetic variation within a population increases chance of survival when there is an environmental change. As some will have characteristics that better adapt them to fit the change. In many organisms the cells are diploid. For sexual reproduction they must produce haploid gametes, so when the two gametes fuse in fertilisation, a diploid zygote is the result.

Question 55

What are homologous chromosomes

Answer 55

Homologous chromosomes are made up of chromosome pairs of approximately the same length, centromere position, and staining pattern, for genes with the same corresponding loci. One homologous chromosome is inherited from the organism's mother; the other is inherited from the organism's father. Although they have the same genes, they have different alleles for the genes.

Question 56

How many divisions are there in meiosis

Answer 56

There are two divisions in meiosis, and in each division there are 4 stages.

Question 57

Describe the events that occur in prophase 1 of meiosis

Answer 57

-the chromatin condenses and each chromosome supercoils. In this state they can take up stains and be seen with a microscope. -the nuclear envolope breaks down, the spindle threads of tubulin form from the centrioles at each pole of animal cells. -the chromosomes come together in homologous pairs Each member of the pair consists of two chromatids -crossing over occurs where non sister chromatids wrap around each other and swap sections of alleles so that alleles are shuffled.

Question 58

Describe the events that occur in metaphase 1 of meiosis

Answer 58

The pairs of homologous chromosomes, still in their crossed over state, attach along the equator of the spindle. -each attaches to the spindle thread by its centromere -the homologous pares are arranged randomly, with the members of each pair facing opposite poles of the cell. This arrangement is indépendant assortment. -the way that they line up in metaphase determines how they will segregate independently when pulled apart during anaphase.

Question 59

Describe the events that occur in anaphase 1 of meiosis

Answer 59

- the members of each pair of homologous chromosomes are pulled apart by motor proteins that pull along the tubulin threads. -the centromeres do not divide, and each chromosome consists of two chromatids -the crossed over ares separate from each other, resulting in swapped areas of chromosome and allele shuffling.

Question 60

Describe the events that occur in telophase 1 of meiosis

Answer 60

In most animals, two new nuclear envolopes form around each set of chromosomes, and the cell divides by cytokinesis. There is then a short interphase when the chromosomes uncoiled. -each new nucleus contains half the original number of chromosomes, but each chromosone consistas of two chromatids. -in most plant cells, the cell goes straight from anaphase 1 into prophase 2.

Question 61

Describe the events that occur in prophase 2 of meiosis

Answer 61

-if the nuclear envolopes have reformed, then they now break down. -the chromosomes coil and condense, each one consisting of two chromatids. -the chromatids of each chromosome are no longer identical, due to crossing over in prophase 1. -spindles start to form

Question 62

Describe the events that occur in metaphase 2 of meiosis

Answer 62

-the chromosomes attach, by there centromeres to the equator of the spindle. -the chromatids of each chromosone are randomly arranged. -the way that they are arranged determines the way they will separate in anaphase.

Question 63

Describe the events that occur in anaphase 2 of meiosis

Answer 63

-the centromeres divide -the chromatids of each chromosome are pulled apart by motor proteins along tubulin threads of the spindle fibres. -the chromatids are therefore randomly separated.

Question 64

Describe the events that occur in telophase 2 of meiosis

Answer 64

-nuclear envolopes form around each of the four haploid nucleus -in animal cells, the two cells now divide to give four haploid cells -in plant cell, a tetrad of four haploid cells is formed.

Question 65

How does meiosis produce genetic variation during division

Answer 65

-crossing over in prophase 1 shuffles alleles -indépendant assortment of maternal and paternal chromosomes of each pair -indépendant assortment of chromatids in anaphase 2 leads to further random distribution of genetic material -haploid gametes are produced, which can undergo random fusion with gametes derived from another organism of the same species.

Question 66

What is differentiation

Answer 66

The process by which stem cells become specialised into different types of cells

Question 67

Describe the specialisation for erythrocytes and neutrophils

Answer 67

Erythrocytes carry oxygen from the lungs to respiring cells and neutrophils ingest invading pathogens These cells are very different from each other but both derive from stem cells in the bone marrow. So how are the erythrocytes adapted to carry out their function: -they are very small, about 7.5 micro meters in diameter, so have a large surface area to volume ratio. This means oxygen can diffuse across there membranes easily and reach all regions inside the cell. Their biconcave shape also increases this SA/V ratio. They are also very flexible. As they have a well developed cytoskeleton which allows then to change shape so they can twist and turn when travelling down narrow capillaries. Aswell as this most of their organelles are lost at differentiation, so they have no nucleus, mitochondria or endoplasmic reticulum, and a very little cytoplasm. This provides more space for the many haemoglobin molecules housed inside them. So how are neutrophils adapted to carry out their function: -they are about twice the size of erythrocytes, and each neutrophil contains a multilobed nucleus -they are attracted to and travel towards infection by chemtaxis -they contain lots of lysosomes which have powerful hydrolytic enzymes to break down foreign matter.

Question 68

How are spermatozoa adapted to their function

Answer 68

-the many mitochondria in carry out aerobic respiration. The ATP provides energy for the undulipodium to move and propel the cell forwards -small and thin so they can move easily -have an acrisome which contains enzymes that digest the outer protective covering of the ovum, allowing the sperm head to enter. -head of the sperm contains the haploid male gamete nucleus and a very little cytoplasm

Question 69

How are epithelial cells adapted to their functioning

Answer 69

Epithelium is the lining tissue that’s makes up the walls of capillaries and alveoli, and line your intestines. The cells are flattened in shape (squamous epithelial cells) and some have cilia (ciliated epithelium)

Question 70

How are palisade cells in plants adapted for their functioning

Answer 70

Palissade cells within leaves are well adapted for photosynthesis because: -they are long and cylindrical, so that they can pack closely together but with little spaces between them for air to circulate -they have a large vacuole so that the chloroplasts are positioned nearer to the periphery of the cell, reducing the diffusion distance for carbon dioxide. -they contain many chloroplasts -they contain cytoskeleton threads to move the chloroplasts nearer t the surface of the cell when light intensity is low.

Question 71

How are guard cells adapted for their functioning

Answer 71

There are pairs of specialised cells called guard cells. -light energy is used to produce ATP -the ATP actively transports potassions ions from surrounding epidermal cells into gaurd cells. Lowering their water potential. -water now enters the gaurd cells from neighbouring epidermal cells, by osmosis. -the gaurd cells swell, but at the tips the cellulose cell wall is more flexible, and its more rigid where it is thicker. The tips bulge, and a gap is formed. -air can then enter the spongy mesophyll

Question 72

How are root hair cells adapted to their functioning

Answer 72

Root hair cells are epidermal cells on the outer layering of young plant roots. - the hair like projection greatly increases the surface area for absorbsion of water and mineral ions, such as nitrates from the soil into which it projects. -mineral ions are actively transported into the root hair cells lowering the water potential within them causing water to follow by osmosis, down the water potential gradient. -the root hair cells have special carrier proteins in the plasma membrane in order to actively transport these mineral ions in. -these cells will also produce ATP needed for active transport.

Question 73

How are xylem and phloem vessels adapted to their functioning

Answer 73

The cells that make up the xylem are adapted to their function: They lose their end walls so the xylem forms a continuous, hollow tube. They become strengthened by a substance called lignin close ligninCarbohydrate material lining the xylem vessels providing strength and support.. The cells that make up phloem have been adapted to their function: sieve tubes, which are specialized for transport and lack nuclei, and companion cells, which are necessary components in the translocation of assimilates. Sieve tubes have perforated ends, so their cytoplasm connects one cell to another.

Question 74

What is the definition of a tissue

Answer 74

A tissue is a group of cells working together to preform a particular function

Question 75

What are the bodys four main types of tisse

Answer 75

Epithelial Connective Muscle Nervous

Question 76

Describe how epithelial tissue is adapted to its functioning

Answer 76

Epithelial tissue covers and lines free surfaces in the body such as the skin, cavities of the digestive and respiratory systems, blood vessels, heart chambers and walls of organs. The characteristics are as follows: -the tissue is made up of almost entirely cells -these cells are very close together and form continuous sheets. Adjacent cells are bound together by lateral contacts, such as tight junctions and desmosomes. -there are no blood vessels within epithelial tissues: cells receive nutrients by diffusion from tissue fluid in the underlying connective tissue. -some epthielal cells have smooth surfaces but some have projections, either cilia or microvilli. -epithelial cells have short cell cycles and divide up to two or three times a day to replace worn or damaged tissue.

Question 77

What are the adaptaptations of connective tissue that improve its functioning

Answer 77

Connective tissue is widely distributed in the body. It consists of a non-living extra cellular matrix containing proteins and polysaccharides. This matrix separates the living cells within the tissue and enables it to withstand forces such as weight. Bone, blood, cartilage, tendons and ligaments are all examples of connective tissue.

Question 78

Describe the types of cartilage and state its components

Answer 78

Immature cells in cartilage are called chondroblasts. They can divide by mitosis and secrete the extracellular matrix. Once the matrix has been synthesised, the chondroblasts become mature, less active chondroblasts, which maintains the matrix. There are three types of cartilage: -Hyaline cartilage- forms the embryonic skeleton, covers the ends of long bones in adults, joins ribs to the sternum. And is found in the nose, trachea and larynx. -fibrous cartilage- occurs in discs between vertibrae in the backbone and in the knee joints. -elastic cartilage-makes up the outer ear and epiglottis (flap that closes over the larynx when you swallow)

Question 79

Describe the properties of muscle tissue and state the types

Answer 79

Muscle tissue is well vascularised. Muscle cells are called fibres: they are elongated and contain special organelles called myofillaments made of proteins actin and myosin. These myofillaments allow the muscle tissue to contract. The types of muscle tissue are: -skeletal muscles- packaged buy connective tissue sheets, joined to bones by tendons; these muscles, when they contract cause bones to move. -cardiac muscles- makes up the walls of the heart and allows the heart to beat and pump blood -smooth muscles- occurs in the walls of intestines, blood vessels, uterus and urinary tracts. It propels substances along.

Question 80

What are the properties of epidermal plant tissue

Answer 80

This is the equivalent to epithelial tissue in animals. It consistes of flattened cells that, apart from guard cells, lack chloroplasts and form a protective covering over leaves, stems and roots. Some cells also have walls impregnated within a waxy substance making up a cuticle. This is particularly important in dryer places as it reduces water loss from leaves.

Question 81

What are the properties of meristematic tissues

Answer 81

Meristematic tissue contains stem cells. It is from this tissue that all other plant tissues are derived from by cell differentiation. It is found at root and shoot tips, and in the cambium of vascular bundles. The cells in meristems have thin walls containing very little cellulose and do not have chloroplasts. They also do not have a large vacuole and can divide by mitosis and differentiate into other cell types.

Question 82

How do xylem and phloem vessels derive from meristems

Answer 82

As most plant cells mature, they develop a large vacuole and rigid cellulose cell wall. These prevent the cell from dividing, however, plants need to grow and produce new cells. New cells arrive at the meristems, by mitosis. Some cambium cells derive into xylem vessels. Lignin is deposited in their cell walls to reinforce and waterproof them. However, this also kills the cells. The ends of the cells then break down so that the xylem forms continuous columns with wide lumens to carry water and dissolved mineral ions. Some cambium cells differentiate into phloem sieve tubules or companion cells. -sieve tubes lose most of their organelles, and sieve plates develop between them. Companion cells retain their original organelles and continue metabolic functions to provide ATP for active loading of sugars into sieve tubes.

Question 83

Name the plant organs

Answer 83

Leaf Root Stem Flower

Question 84

What is the function of the plant organs leaf and roots

Answer 84

Leaf function is for photosynthesis And root functioning is for anchorage in the soil, absorption of mineral ions and water and storgae

Question 85

What is the function of the plant organs stems and flowers

Answer 85

Stem function is for support, holding leaves up for sunlight exposure, transportation of mineral ions and water and profucts of photosynthesis. Flower function is for sexual reproduction

Question 86

What is an organ system (define the term)

Answer 86

A group of organs working together to preform a particular function

Question 87

State the organ systems within the body

Answer 87

Digestive system Circulatory system Respiratory system Urinary system Integumentary system Musculo-skeletal system Immune system Nervous system Endocrine system Reproductive system Lymph system

Question 88

What organs and tissues are involved in the digestive system

Answer 88

Oesophagus, stomach, intestines, associated glands, the liver and pancreas

Question 89

What organs are associated with the organ system respiratory system

Answer 89

Airways, lungs, diaphragm and intercostal muscles.

Question 90

What are the organs ad tissues involved in the circulatory system

Answer 90

Heart and blood vessels

Question 91

What organs and tissues are involved in the urinary system

Answer 91

Kidneys, ureters and bladde

Question 92

What organs and tisses are involved in the integumentary system

Answer 92

Skin, hair and nails

Question 93

What organs and tissues are involved in the musculoskeletal system

Answer 93

Skeleton and skeletal muscles

Question 94

What organs and tissues are involved in the immune system

Answer 94

Bone marrow, thymus gland, skin, stomach acid and blood.

Question 95

What organs and tissues are involved in the nervous system

Answer 95

Brian, spinal chord and nerves

Question 96

What organs and tissues are involved in the endocrine system

Answer 96

Glands that makes hormones, eg. Thyroid, ovaries, testes and adrenals.

Question 97

What organs and tissues are involved in the reproductive system

Answer 97

Testes, penis, ovaries, uterus and vagina

Question 98

What organs and tissues are involved in the lymph system

Answer 98

Lymph nodes and blood vessels

Question 99

Give an example of the life process carried out by the lymph system

Answer 99

Transports fluid back to the circulatory system and is also important in resisting infections

Question 100

Give an example of the life processes carried out by the digestive system

Answer 100

Nutrition to provide ATP and materials for growth and repair

Question 101

Give an example of the life processes carried out by the integumentary system

Answer 101

Waterproofing,protection and temperature regulation

Question 102

Give an example of the life processes carried out by the nervous system

Answer 102

Communication, control and coordination

Question 103

Give an example of the life processes carried out by the urninary system

Answer 103

Excretion and osmoregulation

Question 104

Give an example of the life processes carried out by the immune system

Answer 104

Protection against pathogens

Question 105

Give an example of the life processes carried out by the respiratory system

Answer 105

Breathing and gaseous exchange exertion

Question 106

Give an example of the life processes carried out by the musclulo skeletal system

Answer 106

Support, protection and movement

Question 107

Give an example of the life processes carried out by the endocrine system

Answer 107

Coordination, control and communication

Question 108

Give an example of the life processes carried out by the ciculatory system

Answer 108

Transport to and from cells

Question 109

What are stem cells

Answer 109

Stem cells are undifferentiated cells, capable of becoming any type of cell in the organism. They are described as pluripotent meaning they can express all their genes and divide by mitosis and provide more cells than can then differentiate into specialised cells, for growth and tissue repair.

Question 110

Give 3 sources of stem cells

Answer 110

Embryonic stem cells- these are present in early embryo formed when the zygote begins to divide Stem cells in umbilical cord blood Adult stem cells- found in developed tissues such as blood, brain, muscle, bone, adipose,tissue and skin. Induced pluripotent stem cells- developed in labs by reprogramming differentiated cells to switch on certain key genes and become undifferentiated

Question 111

What are the potential uses of stem cells in research and medicine

Answer 111

Bone marrow transplants- Stem cells from bone marrow are already in extensive use to treat diseases of the blood and immune system. They are also used to restore a patients blood system after traitement for specific types of cancer, where patients bone marrow cells can be obtained before treatment, stored, and then put back inside the patient after treatment. Drug research- If stem cells can be made to develop into particular types of human tissue, then new drugs can be tested first on these tissues rather than animal tissues. Developmental biology- Scientists can make use of stem cells, in many ways, to research developmental biology and enable better understanding of how multicellular organisms develop, grow and mature. They can study how these cells develop to make particular cell types and can learn how each cell type functions and see what goes wrong when they are diseased. Repair of damaged tissues or replacement of lost tissues- It is quite difficult to culture stem cells in a lab, so research into this is ongoing. Also, it is nescessary to find out which cytokine cell-siganlling molecules are needed to direct the differentiation of stem cells into particular cell types. -stem cells have been used to treat mice with type 1 diabetes by programming iPS cells to become pancreatic beta cells. Research is underway to develop such treatment for type one diabetes in humans. -bone marrow stem cells can be made to develop into liver cells and could be used to treat liver disease -stem cells directed to become nerve tissue could be used to treat Alzheimer and Parkinson’s disease or to repair spinal cord injuries. -stem cells may be used to populate a bioscaffold of an organ, and then directed to develop and grow into specific organs for transplanting. This is called regenerative medicine. If the patients cells are obtained, reprogrammed to become iPS cells, and then used to make such an organ, there will be no need for immune suppressant drugs.